1. Field of the Invention
This invention relates to a process of making blocks of bags, which have preferably blocked stubs, which are joined by perforation lines substantially only at the bottom opening-definingedges ofthe individual bags whereas they are separated from the top opening-defining edges by a substantially continuous slit, wherein a tubular film of synthetic thermoplastic is provided in partial regions with perforation holes extending through both plies and slits extending substantially over the width are formed only in the upper ply, whereafter the bags are severed from the tubular film by hot-wire welding and are stacked.
2. Description of the Prior Art
German Utility Model 89 15 077.5 discloses blocks of bags which are joined to stubs by a perforation line only at the bottom wall of each bag and the bags are held together in ablock of bags at said stubs by means of stacking pins or staples, whereas the opening-defining edges of the top plies of the bags terminate in front of the perforation lines defining the stubs. In such blocks of bags the currently uppermost bag of each stack can be opened by an air stream blown into the bag so that objects to be packaged in the bag, such as bread, can be pushed into the bag and that pushing will also cause the bag to be torn off along the transverse perforation line from the stack holder and from the stub. Similar blocks of bags can be made by a process which will be described hereinafter with reference to FIG. 1 of the drawing. A flat web 1 is reversely folded to form a doubled web 2, which is formed with a bottom fold 3 in known manner. To that end the bottom ply of the flat web 1 is reversely folded so that the two edges 4 and 5 are offset from each other and a top edge strip 6 is left exposed. That exposed strip is formed with suspension holes 7. Adjacent to said suspension holes the strip 6 has slits 6, which extend inwardly from the outside and terminate short of the suspension holes 7. The individual bags are then severed by slits 9 made by hot-wire welding and are subsequently combined by known means to form a block of bags 10. Wire loops 11 are inserted through the suspension holes 7 and plugs 12 are slidably fitted on the free ends of the legs of each wire loop. Such block of bags differ from the one disclosed in the above-mentioned German Utility Model 89 15 077 in that the top strips, which serve to retain and stack the bags, are also torn off when the individual blocks are torn off.
Published German Patent Application 36 37 231 discloses a process of making blocks of bags of the kind described first hereinbefore. A special problem arising in such process resides in that it is difficult to form only the bottom or ply, which will form the rear walls of the bags, with transverse perforation lines joining the bags of the stack to the stubs whereas the top plies, which in the stack constitute the forward walls of the bags are entirely or almost entirely separated by transverse slits from the tubs, which serve to stack and retain the bags. Because the front walls of the bags are separated from the stubs, the currently uppermost bag of a stack can subsequently be opened, e.g., by being inflated, when the bag is to be filled.